Apparatus for tensioning strip material



Nov. l6, A. B. WILSON AiPARATUS FOB TENSIONING STRIP MATERIAL FiledSept. 7, 19M 2 Sheets-Sheet l INVENTOR Abram BJ Vi/son A. B. WILSON2,454,021

APPARATUS FOR TENSIONING STRIP MATERIAL Nov. 16, i9 3 Filed Sept. 7,1944 2 Sheets-Sheet 2 IIII I VARIABLE VOLTAGE ARMATURE CIRCUIT M F 1k wwG T F lvvvi p F M- MAIN LINE CONTACTOR acoIL .CON' CURENT A-- AMMETERBEGUMTOR R F SERIES FIELD i DMrSI-T F 'j M.M.MAIN MOTOR 0%. F vG.D.C:-D.C.GENERATOR EX .SF DNA-DRAG MOTOR Ex. ExcIToR MM- R -VARIABLERHEOSTAT i I S.F.-SHUNT FIELD GDQSE ST fun I START M STOP M INVENTORFIELD AND CONTROL CIRCUIT llbram'B'wllson Patented Nov. 16, 1948APPARATUS FOR TENSIONING STRIP MATERIAL Abram B. Wilson, Hollidays Cove,W. Va absignor to National Steel Corporation, a corporation of DelawareApplication September 7, 1944, Serial No. 552,974

Claims. (01. 271-23) This invention relates to the tensioning of stripwhile being processed in strand form.

In order to achieve high rates of production and the low unit costthereby made possible, metal strip, e. g., steel strip, is now beingprocessed to a large extent in the form of a continuous strand orribbon, instead of after being cut into lengths. The apparatus forsubjecting strip to various processes frequently has a length of severalhundred feet and the strip is fed through the apparatus at a. high rateof speed. Tensioning devices appropriately located have been employedfor insuring proper travel of the strip through the apparatus. Thesedevices, as constructed hereto- I fore, have been characterized inoperation by a marked tendency of the strip to weave from side to sidetherein. If unchecked, this tendency may cause the fouling of the stripedges on the processing apparatus resulting in damage to the materialand possibly jamming the entire apparatus, necessitating a lengthyshut-down for the removal of damaged strip, readjustment of theapparatus and again starting the processing operation. It is evidentthat the risk of such delays constitutes a, serious threat to the highproduction rate which is the only justiflcation for the expensiveinstallations necessary for processing strip in strand form.

I have invented a novel method and apparatus for tensioning strip whichavoid the tendency toward side-wise weaving exhibited by the tensioningapparatus known previously. In a preferred embodiment of the apparatus,1 provide one or more tensioning rolls so positioned that the stripwraps around a substantial portion of the periphery thereof. A pressureroll cooperates with one of the tension rolls to grip the stripfrictionally therebetween. The tension roll with which the pressure rollcooperates has a convex contour or a crown. That is to say, the roll isslightly larger at the middle than at the ends and tapers progressivelyfrom the middle toward the ends. The pressure roll may be trulycylindrical but the efiectiveness of theapparatus in eliminatingsidewise weaving is improved if the pressure roll has a crown similar tothat of the tension roll. In either case, the pressure roll and thetension roll cooperating therewith exert a frictional grip on the stripprincipally adjacent the center, leaving the strip edges unstressed, or,in any event, stres sed to an extent much less than the central portion.

A clear understanding of the invention may be had from a considerationof the following detailed description referring to the accompanyingdrawmg: illustrating a preferred embodiment and practice. In thedrawings,

Figure 1 is a central section through a tensioning apparatus of myinvention on a plane normal to the axes of the tension and pressurerolls; and

Figure 2 is diagrammatic view showing the convex contour of the pressureand tension rolls to an exaggerated degree.

Figs. 3 and 4 illustrate conventional means for controlling the tensionrolls.

Referring in detail to the drawings, my tensioning apparatus indicatedgenerally at I0 comprises spaced housings l I between which the stripbeing processed, designated I2, is adaptedto pass.

' On the entering side of the apparatus, an entry guide roll I3 isJournaled in bearings i4 secured to the housings. A deflector roll I! isjournaled in bearings ISa carried on arms I8. The arms are pivoted forangular movement on brackets l'l secured to the housings. A seconddeflector roll i8 is Journaled in bearings is adjustable transversely ofthe apparatus on rails 20 extending between the housings.

The path of the strip l2, as indicated in chain lines, is over the guideroll i3, under the deflector roll i5, over the second deflector roll l8and thence between a pressure roll 2| and an upper tension roll 22. Thepressure roll is journaled in chucks 23 adjustably mounted in thehousings. The tension roll 22 is similarly journaled in chucks Afterpassing between the rolls 2i and 22, the strip wraps around the latterand then around a lower tension roll 25 journaled in chucks 2B. Thetension rolls have shields or jackets 21 extending around the portionsthereof engaged by the strip. From the lower tension roll 25, the strippasses over an exit guide roll 28 journaled in bearings 29.

The upper tension roll 22 with which the pressure roll 21 cooperates hasa convex or crowned contour, as shown in Figure 2, to an exaggerateddegree. The illustrated embodiment of the invention is intended for usein an electrolytic striptinning apparatus, and all the rolls include ametal body 22a and a rubber sheath thereon to protect the coatedmaterial from abrasion. The sheath 22b is ground slightly larger, say.030", at the middle than at the ends and with acontour which tapersprogressively from the middle to the ends.

The provision of an upper tension roll having a slight crown, such asthat indicated, has been found effective to reduce materially the extentof side-wise weaving of the strip as it progresses.

- 3 In order to eliminate weaving, for all practical purposes, thepressure roll 2i should also have a crown similar to that of the uppertension roll, viz. about .030".

It will be apparent from a consideration of Figure 2 that when thepressure roll'2l is ad- Justed relative to the tension roll 22, so as togrip the strip therebetween, the cooperating rolls exert a frictionalforce principally on the central portion of the strip, leaving the edgeportions relatively free and unstressed, or, at any rate, under atension much less than that exerted on the central portion. The width ofthe central portion of the strip to which the tension is principallyapplied by friction, of course, varies with the pressure exerted by theroll 2i. This pressure naturally varies with the operating conditionsexisting in the particular processing apparatus to which the inventionis applied. For obvious reasons, the tension on the strip is kept at thelowest value sufilcient to effect a desired travel of the strip throughthe apparatus. It will be understood that the apparatus shown in thedrawings is intended to exert back tension on the strip, but theprinciple of the invention may also be incorporated in the apparatus forpulling the strip through the processing equipment. The operation of thetensioning apparatus is controlled in usual manner by means independentof the strip, e. g., by motor drive or generator drag, which may beapplied to one or more of the rolls, preferably the tension rolls. Suchmeans are shown in the Stafford Patent 2,315,459 and the TaylersonPatent 2,338,143.

Figures 3 and 4 illustrate conventional means for controlling thetension rolls. An electric motor 30 is connected to the roll 22 by gears3| and 32. This motor may be driven by a source of electricity so as tosupply tension to the strip or it may be driven by the strip. in whichcase it acts as a generator and imposes a drag on the strip. Figure 3shows the motor 30 connected to a source of current and operated to pullthe strip through the tensioning apparatus. Figure 4 is an electricaldiagram showing electrical connections whereby the motor 30 can bedriven by the strip and operated as a generator to impose a drag on thestrip. The motor 30 designated DM on the wiring diagram of Figure 4 isa. constant speed electric motor which is overdriven by the strip at ahigher rate than its normal speed so that it is forced to act as anelectric generator and thus resist the forward movement of the strip.Various types of electric motor and wiring arrangements may be employedas will be readily understood by one skilled in the electrical art. Thiselectric motor is preferably adapted to run at a constant speed with aconstant load and to vary in torque directly with variations in thecurrent input. The motor 30 may be constructed and connected so that ittends to drive the strip at a rate of, say, 75% of that at which anothermotor used to pull the stripthrough the strip processing apparatus (thissecond motor is designated MM in Figure 4), draws the strip forward. Themotor initially aids in moving the strip while the strip processingapparatus is being started up; but when the strip is moving at fullspeed, the motor is overdriven and becomes a generator of electricityand so applies a counteriorce which resists the forward movement of thestrip. The faster .the strip moves, the greater is this countertorqueapplied by the motor generator to increase the tension on the strip. Themotor 30 has the same general characteristics as the motor M with whichit is connected in parallel in a constant voltage D. C. circuit. Thedirect current generator G. D. C. in the variable voltage armaturecircuit is driven by a suitable constant speed motor. This serves todrive the direct current motor MM and the direct current motor DM atconstant speeds when the current is held constant. An exciter EXdevelops a direct current of constant amperage for the shunt fieldswhich control the speeds of the two motors and the direct currentgenerator. A constant current regulator of standard construction whichmechanically interconnects the armature circuit and the shunt fieldcircuit serves to maintain a constant current in the shunt fieldcircuit, and this may be further regulated as desired by the variablerheostat R. Suitable mechanism may be employed to start and stop themotors as illustrated in the diagram, and this may be of any standardconstruction and need not be here described. By adjusting the rheostatR, the shunt field of the tension motor may be varied to change thespeed of that motor and thereby vary the back pressure or thelongitudinal tension on the strip. After this adjustment has been made,then that tension will remain uniform because of the constant currentdeveloped in the circuit. That is. if the speed of the main motor MMremains uniform, then the current in the shunt field remains uniform andthe tension on the strip does not change.

The outstanding advantage of the invention, as already stated, is thereduction or elimination of the tendency of the strip to weave side-wisein its travel through the tensioning device. This obviates thepossibility of fouling of the strip on the sides of the processingapparatus and the resulting damage to the strip or the stoppage of theprocessing apparatus. A further advantage resides in the fact thatexisting tensioning devices may be easily modified to operate on theprinciple of my invention. Little or no additional cost is involved ingrinding the rubber sheaths of the pressure and upper tension rolls to aconvex or crowned contour instead of to a truly cylindrical surface.

Although I have illustrated and described but a preferred embodiment ofthe invention, it will be recognized that changes in the details ofconstruction may be made without departing from the spirit of theinvention or the scope of the appended claims.

I claim: I

1. Apparatus for exerting a tension on strip comprising a tension roll,means for guiding the strip around the roll in frictional contact with asubstantial portion of the periphery thereof, and a pressure rollcooperating with the tension roll to grip the strip therebetween, saidrolls having a convex contour.

2. Apparatus for exerting a tension on strip comprising a tension roll,means for guiding the strip around the roll in frictional contact with asubstantial portion of the periphery thereof, and

.a pressure roll cooperating with the tension roll to grip the striptherebetween, said rolls.tapering progressively from the middle towardboth ends.

3. In metal strip processing apparatusin which metal strip is drawnlengthwise through substantial distances and tends to weave from side toside, means for controlling the movement oi the strip through theapparatus and counteracting said tendency and insuring proper trackingof the strip, said means comprising a roll, means for guiding the stripas it moves through the apparatus so that it passes about and in contactwith a substantial portion of the periphery of said roll, a pressureroll cooperating with said first mentioned roll to grip the strip, saidrolls being cooperatively contoured so that the strip is grippedtherebetween with greater pressure adjacent the center of the strip thanadjacent the edges of the strip, and means independent of the strip forcontrolling rotation of at least one of said rolls.

4. In metal strip processing apparatus in which metal strip is drawnlengthwise through substantial distances and tends to weave from side toside. means for controlling the movement of the strip throughtheapparatus and counteracting said tendency and insuring propertracking of the strip, said means comprising a roll, means for guidingthe strip as it moves through the apparatus so that it passes about andin contact with a substantial portion oi the periphery oi said roll, apressure roll cooperating with said first mentioned roll to grip thestrip, at least one of said rolls having greater diameter adjacent itscenter than adjacent its edges so that the strip is gripped between saidrolls with greater pressure adjacent the center of the strip thanadjacent the edges of the strip, and means independentoi the strip forlcontrolling rotation of said first mentioned rol 5. In metal stripprocessing apparatus in which metal strip is drawn lengthwise throughsubstantial distances and tends to weave iro side to side, means forcontrolling the movement of the strip through the apparatus andcounteracting said tendency and insuring proper tracking of the strip,said means comprising roll means engaging the strip as it moves throughthe apparatus so that the strip is in substantial surface contact withsaid roll means and means independent of the strip for controllingrotation of said roll means, said roll means being contoured togrippingly engage the strip more tightly adjacent the center of thestrip than adjacent the edges of the strip.

ABRAM B. WILSON.

REFERENCES CITED The following references are of record in the file ofthis patent:

2 UNITED STATES PATENTS Number Name Date 1,142,442 Krauth ..'June 8,1915 1,419,049 Harsel et al June 6, 1922 1,998,931 Kellogg Apr. 23, 19352,102,793 George Dec. 21, 1937 2,240,265 Nachtman Apr. 29, 19412,297,380 Klein et a1 June 23, 1942 2,316,801 McLaughlin et al. Apr. 20,1943 FOREIGN PATENTS Number Country Date 432,622 Germany Aug. 24, 1926

